Many chemical building blocks and energy sources are derived from fossil carbon deposits that are extracted from the earth's crust in the form of crude petroleum, coal, or natural gas. These fossil carbon deposits range from materials with low carbon to hydrogen ratios such as methane to those that are nearly pure carbon, such as certain types of coal. Fossil carbon sources are viewed as being non-renewable because it is estimated that such deposits take millions of year to form through slow anaerobic decomposition of buried organic matter in combination with exposure to heat and pressure.
World energy consumption is expanding at a rate of over 2% per year. In addition, the demand for products that are made from materials (including many types of polymers) derived from fossil carbon sources continues to increase at an accelerating pace. As such, while the total amount of fossil carbon deposits continues to change as new deposits are discovered, the amount remaining for further exploitation (whether currently known or unknown) necessarily decreases at an accelerating pace.
In addition, most uses of fossil carbon sources lead to a net increase in the amount of carbon in the atmosphere (usually in the form of carbon dioxide) because the cycle starts with carbon that is safely sequestered in the earth's crust and ends with carbon in the atmosphere. This is significant because carbon dioxide has been identified as a key contributor to global warming.
In addition, fossil carbon sources are not evenly distributed within the earth's crust. Some geographic areas are relatively rich in fossil carbon sources while others are relatively poor in fossil carbon sources. In some cases, certain areas may have a substantial amount of one form of fossil carbon but be substantially deficient in other forms. This uneven distribution results in substantial geopolitical stress as countries that are deficient in such essential resources sometimes find that they are at the economic mercy of countries that are rich in such resources.
Utilizing carbon from renewable sources such as organic matter can reduce carbon emissions substantially on a net lifecycle basis because the carbon in emissions from the combustion of renewable carbon sources is from carbon that was previously already in the atmosphere and incorporated into organic materials, rather than being permanently sequestered in the earth's crust.
However, carbon from renewable sources generally does not exist in the same forms as fossil carbon sources and this creates issues. For example, the energy and chemical production infrastructure of most nations has been built up to use fossil carbon sources and cannot be easily changed over to rely on renewable sources. In addition, the same range of compounds found in fossil carbon sources is generally not observed in most renewable carbon sources.